Flue gas cleaning plants for, inter alia, coal-fired and oil-fired power stations, waste incineration plants etc. often have what is referred to as an SCR reactor. An SCR (Selective Catalytic Reduction) reactor involves a reactor in which a catalytically induced, selective reduction of nitrogen oxides occurs. The SCR reactor has a catalyst, which often is configured as a honeycomb structure or as a number of closely spaced plates to provide a maximum reactive surface. A drawback in many SCR reactors is that particulate dust, which is formed in the burning of, for instance, coal, oil or waste, gets stuck in the SCR reactor and clogs it.
U.S. Pat. No. 5,687,656 in the name of Kaneko et al discloses a method of reducing the amount of dust that reaches and clogs an SCR reactor. In the method according to U.S. Pat. No. 5,687,656, a flue gas is first passed in a horizontal flue gas duct, then in a vertical flue gas duct and subsequently through a porous plate, which has a pore size smaller than the particles that are to be separated.
The method according to U.S. Pat. No. 5,687,656 may cause a reduction of the amount of dust that reaches the SCR reactor. A problem with this porous plate, however, is the risk of it being clogged by dust particles. Such clogging causes an increase in pressure drop and, thus, increased operating expenses.